Power-hammer



'0. B. COATES.

POWER HAMMER.

APPLICATION FILED FEB. 6, 1920.

Patented J 11116 28, 192 1.

- 3 SHEETS-SHEET I C. B. COATES.

POWER HAMMER.

APPLICATION FILED FEB-5,1920.

C. B. COATES.

POWER HAMMER.

APPLICATION FILED FEB.G,1920A 1,882,821 Patented June 28, 1921 I 3SHEETS-SHEET 3.

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UNITED STATES PATENT OFFICE.

CHARLES B. COATES, OF CHICAGO, ILLINOIS, 'ASSIGNOR TO CHICAGO PNEUMATICTOOL COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF NEW JERSEY.

POWER-HAMMER.

Specification of Letters Patent.

Patented June 28, 1921,

Application filed .Febrnary 6, 1920. Serial No. 356,601.

T 0 all whom it may concern:

Be it known that 1, CHARLES B. CoA'rEs, a citizen of the United States,residing at Chicago, in the county of Cook and, State of Illinois, haveinvented certain new 'and'useful Improvements in Power-Hammers, of whichthe following is a specification.

My invention relates to percussive power hammers operated preferably,though not necessarily, by an electric motor as the prime mover andadapted to hammer purposes, such as chipping, drilling, riveting or thetamping of broken stone or.similar ballast by means of a chisel, drill,rivet set, tamper bar, or the like, to one end of which the strikingmember such as the hammer piston of the power hammer imparts its blow.The Ol)]8(3t of my invention is to provide a simple, efiicient andreliable machine of this type, characterized more particularly by theemployment of a compression chamber through which high pressure air isintermittently introduced or in which it is produced by a compressionpiston directly reciprocated by the electric or other type of'motor, incombination with means whereby such high pressure air is dischargedagainst a hammer piston operating in a cylinder or barrel, such airbeing so discharged when it is at its maximum pressure and after thehammer piston has start ed on its downward movement to strike the blow,thereby causing such hammer piston to deliver quick and powerful blowsupon the inner end of the shank of the working tool inserted into thefront end of the barrel.

Other features of advantage and utility in my power hammer will beapparent from the description hereinafter given.

In the drawings Figure 1 is a central sectional elevation of my powerhammer: Fig. 2 a section on the line 22 of Fig. 1; Figs. 3 and 4horizontal sections on the lines 3* and 4;4: respectively of Fig. 1:Figs. 5, (l and. 7 sectional elevations of the compression cylinder andhammer cylinder and their pistons, showing the moving parts in differentpositions during a cycle of operation; Figs. 8, 9, 10 and 11 sectionalelevations of a moditied form of construction and illustrating theposition of the compression piston and hammer piston in differentrelative positions during a cycle of operation; and Fig. 12 a detailedview of a modified form of construct on more particularly of thecompression piston.

My hammer is a power hammer operated preferably by a prime mover locatedin the hammer structure itself and while any suitable motor may beemployed as such prime mover, I prefer an electric motor because it isthe most convenient and compact and also the most desirable becauseelectric current which is avallable everywhere can be supplied theretoat any distance through cables,

My invention will therefore be described in connection with an electricmotor located in the hammer structure itself as the prime moverwithoutintention of limitation thereto. Moreover, I prefer to employ in myhammer a reciprocating compression piston as the means for producing thehigh pressure air intermittently required for the operation of myhammer. but it will be understood that my invention in its broaderaspect is not to be limited to this particular ty )e of means forproducing such pressure.

eferring to the particular embodiment of my invention as illustrated inFigs. 1 to 7 the power hammer comprises the motor structure and casingtherefor at the upper or rearward end thereof to which is-attached agear case and also a compression and hammcr casing and a cylinder orbarrel. To the casing there is also attached a suitable handle or gripfor handling and operating the hammer.

Referring to the details of construction as shown particularly inFig. 1. the motor frame or casing 1 which is of s lble size and shapecontains a suitable electric motor 2. This motor has an armature shaft 3hearing in the end plate 4 clamped against one .cnd oi' the casing 1 andformed at its outer end as a pinion 5 which meshes with a gear (3secured to the crank shaft T. This crank shaft operates within a gcarcase formed by the platc -l and an outer parallel plate 8 and has itshearings in said plates. This crank is also provided with acountcrl)alance i).

The handle 10 which is here of a shape to receive the grip of the handof the operator and to be thereby handled and directed in the work issecured in suitable manner to the motor casing and to the gear casing.This handle contains the electric motor switch indicated generally at 11and is provided with a button 12 for convenient operation of the switch.

To the motor casing and gear casing is secured in suitable manner as bymeans of the bolts 13 a casing 14 containing two chambers 15 and 16arranged side by side or in parallel planes. The chamber 15 is thecompression chamber and within it operates the compression piston 17which is directly connected. to the crank shaft 7 by means of theconnecting rod 18 whereby the piston 17 is reciprocated by the electricmotor. This compression chamber is provided with a lateral air inletport 19 through which atmospheric air is admitted when the piston 17 hasmoved upwardly to a position to clear and uncover such port. The aircompressed by this piston is discharged through a bottom discharge port20 entering into the other chamber as now to be explained.

Within the chamber 16 there is secured in suitable manner as by screwthreading thereinto the hammer cylinder or barrel 21. The upper orrearward end of this cylinder enters a considerable distance into thecasing 14 and the piston chamber of this cylinder 21 may therefore besaid to overlap the compression chamber 15. At a point coincident withthe wide discharge port 20 the threads of the chamber 16 and of thecylinder 21 are cut away to thereby form an annular groove 22 whichcommunicates with the piston chamber 23 of the cylinder 21 by means of aseriesof radial ports 24.

Within the piston chamber there reciprocates a hammer piston 25 which isadapted'on its forward stroke to strike the shank of the working tool 26which is inserted in the front end of the hammer cylinder and on itsrearward or upward stroke to pass upwardly beyond the line of ports 24and into a cushioning space formed therebeyond in the rearward end ofthe piston chamber. By preference means are provided for supplying highcompression air on the top or rear end of the piston when it is in thiscushioning space. If desired the piston could have a loose fit in thepiston chamber above the line of ports 24 but I prefer to employ themeans as shown in Fig. 1. These means consist of a small port 27 leadingupwardly from one of the ports 24 longitudinally through the wall of thehammer cylinder and into the extreme rear end of the piston chamber. Bypreference this end of the chamber is counterbored as indicated at 28 inorder to provide for the unrestricted flow of the compressed air fromthis passage27.

The hammer cylinder 21 is provided at a point intermediate its lengthwith an exhaust port 29 preferably closed by a suitable check valve 30which is here a at valve in the form of a spring secured to the hammercylinder by the screw 31. The hammer'cylinder is also provided near itslower end with a permanently open exhaust port 32.

Describing a cycle of operation and beginning with the hammer parts intheir rear position as shown in Fig. 5 at which time the crank to whichthe rod 18 is connected is in its uppermost position, it will be notedthat at this time the compression piston 17 is also in its uppermostposition and with its lower face above the inlet port 19 whereby thecompression cylinder below the piston is permitted to be filled with airat atmospheric pressure. At this time the hammer piston 25 is near theupper end of its piston chamber and its body covers and closes the ports24.

As the compression piston 17 descends the air below is compressed to ahigh degree. During this compression stroke of the piston 17, averysmall amount of air has passed through the small passage 27 andinitiated the return movement of the hammerpiston on its power stroke.The upper or rear end of the hammer piston reaches the port or ports 24at approximately the instant of maximum compression in the compressionchamber as shown in Fig. 1. At this instant the entire charge of thishigh pressure air is admitted through the series of ports 24 against theupper end of the hammer piston, causing it to be driven downwardly orforwardly against the tool shank with great force and delivering aneffective, snappy, and powerful blow.

Fig. 6 shows the crank pin of the crank shaft advanced slightly beyondthe lower- ,most point after it has passed the lower crank position andstarted 011 its upward stroke. The hammer piston is shown with out anarrow in order to indicate that it is now in a neutral position and theinterval between the crank positions shown in Figs. 1 and 6 representapproximately the crank angle or interval during which the blow isstruck.

The compression cylinder 15 is of very much larger diameter than thehammer piston chamber 23 and relative strokes of the compression pistonand the hammer piston aresuch that the displacement of the compressionpiston is much greater than the displacement of the hammer piston. Thisresults in a considerable terminal pressure acting on the upper end ofthe hammer piston when the blow is struck. This excess pressure aboveatmospheric pressure raises the check valve 30 and the air in thecompression 'chamber and the hammer piston chamber above the upper endof the hammer piston, is reduced to atmospheric pressure, after whichthe check valve closes.

Fig. 7 shows the crank at an angle of 90 degrees on its upward strokeanddue to the rarefication of the air below the comdue to theconsiderable vacuum created in both of their chambers.

As the upper end of the hammer piston passes the ports 24 on its upwardmovement, there is some compression above it due to the air being unableto leak out rapidly enough through the passage 27. Thisresults in thecushioning of the hammer piston at the upper end of its stroke. s

It is obvious that the compression piston being actuated positively bythe crank shaft and the hammer piston belng controlled on its upwardstroke by vacuum created by the upward movement of the compressionpiston, the hammer piston willlag somewhat in its movement behind thecompression piston and the hammer piston will be stopped in its upwardmovement at approximately the point shown in Fig. 5. It will be notedthat the hammer piston acts as a valve to close the discharge port orports of the compression chamber until practically full compression isattained and that it does not receive the charge of this highcompression air until it is actually moving downward on its powerstroke.

As shown in Fig. 1 the center of the grip of the handle 10 is in linewith the center line indicated by the broken line 33-33 which passesthrough the center 'of the power cylinder and working tool and alsoapproximatelythrough the center of gravity of the complete hammer whichis a distinct advantage inasmuch as it provides a perfectly balancedtool while being handled and also applied to the work.

In Figs. 8 to 11 I have shown a modified form of construction in whichthe compression chamber and hammer piston chamber insteadof being placedin parallel are arranged concentrically and with the compression pistonprovided with a central bore to act as a continuation of the hammerpiston chamber. As shown the hammer cylinder 34 has formed integraltherewith at its upper end a compression cylinder 35 forming therewithinthe compression chamber 36. The cylinder 34 has a piston chamber 37within which reciprocates the piston 38. The compression piston 39 isprovided with .a central bore 40 which is in line with the bore orchamber 37 and into which the piston on its upward movement passes. Thechamber or space 40 may therefore be said to constitute a part or acontinuation of the piston chamber 37 and to overlap the compressionchamber 36 in the same general sense as in the construction previouslydescribed. The mode of operation is substantially the same as abovedescribed in connection with the other form of construction with theexception that in this modified form a leakage of air is provided at 41be tween the piston and the chamber 40 for the admission of a smallquantity of compressed air from the chamber 36, in order to initiate thedownward moyement of the piston after it has entered the chamber orpocket 40 which acts as a cushioning chamber.

In Fig. 12 I have shown another modified form of construction which issimilar to that illustrated'in Figs. 8 to 11 with the exception that thepressure against the rear end of the. piston to initiate its return isnot provided by the compression chamber 36 but by separate meansconsisting of a reciprocating piston 42 which is connected by means ofthe rod 43 with the crank shaft of the motor and is adapted toreciprocate in a central bore 44 of the compression piston 45. Themechanism is so timed that after the piston- 46 has entered the bore 44the piston 42 will move downwardly toward the piston 46 and compress theair in the space between these two pistons with the result that thepiston 46 will be initiated in its movement on its downward or powerstroke. In this construction the piston 45 is connected to the crankshaft by means of a pair of arallel rods 47.

claim:

1. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating with the piston chamber, means for intermittentlycompressing the air in such compression chamber to a high or workingpressure, said two chambers having communicating ports, one being alwaysopen to supply compressed air to initiate the movement of the piston onits power stroke and the other being intermittently open so as to causea discharge of high pressure air against the hammer piston after it hasstarted on its power stroke.

2. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating. with the piston chamber, said piston beingadapted to close such communication on its return stroke, means forsupplyinga restricted amount of compressed air from said chamber againstthe piston toinitiate its movement on its power stroke, and means forintermittently compressing the air in such compression chamber to a highor working pressure which is admitted against one end of the pistonafter it has moved on its power stroke to a position to open suchcommunication.

3. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer/piston reciprocable in such chamber, a compressionchamber communicating with the piston chamber, means for intermittentlycompressing the air in such compression chamber to a high or workingpres sure, said two chambers being connected so as to cause a dischargeof high pressure airpression chamber, to a high or working'pressure,said two chambers having a connecting port intermediate the length ofthe piston chamber so as to cause a sudden discharge of high pressureair against the piston to provide the energy for its power stroke, meansproviding a pocket to receive the piston after its extreme rearwardstroke, and means for admitting air under pressure from the compressionchamber to the pocket behind the-piston to initiate its return movement.

5, In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a com ressionchamber communicating with the plston chamber, and a compressing pistonfor intermittently compressing the air in such compression chamber to ahigh or working pressure, said compression chamher being longer than thestroke of its piston to provide'at one end a space for the high pressureand said hammer piston being arranged to govern the communicationbetween the two chambers, closing the same during the time of suchcompression and opening the same at the time of such high compression tocause the air pressure to act upon the piston on its power stroke.

6. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating with the plston chamber, a power operated pistonreciprocating in such compression chamber,- such latter chamber havingan inlet air port governed by such power piston and bein adapted todischarge the compressed a1r through a discharge port communicating withthepiston chamber, said hammer piston being arranged to govern suchdischarge port which is located at the extreme end of the co ressionchamber and through which the compressed air is discharged afterstroke.-

7. In a power hammer, the combination of a cylinder having a pistonchamber, a piston reciprocable therein, a second cylinder having acompression chamber communicating with the piston chamber andoverlapping the same, that portion of the piston chamber which overlapsthe compression chamber acting as a pocket to receive the piston on itsrearward stroke, and means for compressing the air in the compressionchamber, said piston governing the communication between the twochambers and acting to admit the compressed air against its rearward endfor the power stroke of such piston.

8. In a power hammer, the combination of a cylinder having a pistonchamber, a piston reciprocable therein, a second cylinder having acompression chamber communicating with the piston chamber andoverlapping the same, that portion of the piston chamber which overlapsthe compression chamber acting as a pocket to receive the piston on itsrearward stroke, and means for compressing the air in the compressionchamber, said piston governing the communication between the twochambers and acting to admit the compressed air against its rearward endfor the power stroke of such piston, said two chambers being arranged inparallel planes and having a lateral communicating passage for thecompressed air.

9. In a power hammer, the combination of a cylinder having a pistonchamber, a piston reciprocable therein, a second cylinder having acompression chamber communicating with the iston chamber and overlappingthe same, t iat portion of the piston chamber which overlaps thecompression chamber acting as a pocket to receive the piston on itsrearward stroke, and means for compressing the air in the compressionchambpr, said piston governing the communication between the twochambers and acting to admit. the compressed air against its rearwardend for the power stroke of such piston and means for admitting a smallquantity of the compressed air from the compression chamher to saidpocket and behind the piston.

I 10. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating with the piston chamber, and means forintermittently compressing the air in such compression chamber to a highor working pressure, the said piston being arranged to govern thecommunication between the two chambers, closing the same during the timeof such compression and opening the same at the time of such highcompression to cause the air pressure to act upon the piston on itspower stroke, said piston chamber the hammer piston has started on itspower having intermediate its length an exhaust port controlled by saidpiston.

11. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating with the piston chamber, and means forintermittently compressing the air in such compression chamber to a highor working pressure, the said piston being arranged to govern thecommunication between the two chambers, closing the same during the timeof such compression and opening the same at the time of such-highcompression to cause the air pressure to act upon the piston on itspower stroke, said piston chamber having intermediate its length acheck-valve governed exhaust port controlled by said piston.

12.111 a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating with the piston chamber, and means forintermittently compressing the air in such compression chamber to a highor working pressure, the said piston being arranged to govern thecommunication between the two chambers, closing the same during the timeof such compression and opening the same at the time of such highcompression to cause the air pressure to act upon the piston on itspower stroke, said piston chamber having intermediate its length anexhaust port which is uncovered by the rearward end of the piston on itspower stroke.

13. In a power hammer, the combination of a cylinder having a pistonchamber, a hammer piston reciprocable in such chamber, a compressionchamber communicating with the piston chamber, and means forintermittently compressing compression chamber to a high or workingpressure, the said piston being arranged to govern the communicationbetween the two chambers, closing the same during the time of suchcompression and opening the same at the time of such high compression tocause the air pressure to act upon the piston on its power stroke, saidpiston chamber. having intermediate its length an exhaust portcontrolled by said piston, and an always 0 en exhaust port at the frontend of-the piston chamber.

CHARLES B. COATES.

the air in such

